I would probably remake it in the mm2 engine, maybe "COMBINE!" them, since there are the gates to another world, in mm1.
so use the gfx from mm2 to start with, and maybe add extra special for mm1 stuff.

That was the idea 10 years ago lol.
There is text and stuff programmed into the exe for mm2 for inn(s) etc.
All of which can be patched, but is a bit of work.

When I did the mm2 WHDLoad, I just patched the exe via the slave for the copy protection. might play around when I have more of this Mythical free time.

They're not the same, sort of similar.
Items and monsters are stored in mm1's exe. at least in the PC version.
mm1 monsters has a max of 16 characters for names, while mm2 has only 14.
so some monster will need renaming.

MM1's items didn't have a plus as a seperate stat, so the items were 'short sword +2' and 'short sword'.

while mm2 has just a short sword, and you can add a plus of upto +64 from memory.